A drive device using an H-bridge drive circuit, has been known as a drive device that drives a motor including a coil. The motor drive device using the H-bridge drive circuit, includes four switching elements diagonally connected to the motor to cross each other, and turns the switching elements ON or OFF in a predetermined duty cycle so that the operation state of the motor (positive rotation, negative rotation, and stop) can be controlled.
In making a switch from the operation state of the positive rotation or the negative rotation to the state of the stop, energy that has been stored and remains in the coil in the motor, is required to be discharged, and thus a method described below has been known. Refer to Patent Literature described below.
Four switching elements all are turned OFF, and a diode arranged in parallel between the drive terminals of each switching element is used to apply a bias in the forward direction between the drive terminals of each switching element through each body diode so that energy stored in a coil is discharged to the power source side through each diode.
For example, it is assumed that a motor is suddenly and excessively loaded. When the motor being loaded is left, the drive circuit thereof may break down thermally or electrically. Therefore, in a case where a load drive device or a load drive circuit detects the state where the overload has been applied, energy in the load, for example, inertial energy is required to be promptly discharged to the outside of the drive device or the outside of the circuit. The present inventors have found that, that is, control is required to be performed, for example, kinetic energy is converted into electrical energy at the point in time when the overload is detected and then the electrical energy is further converted into thermal energy, or the electrical energy is stored into a capacitor provided in the circuit.